JP2001517017A - Method and apparatus for transmitting data on multiple carrier systems - Google Patents

Abstract

A method in an apparatus for transmitting data in a multi-carrier system includes encoding data and distributing the resulting encoded symbols for transmission at different frequencies. The transmitter includes a control processor (50) that determines a capacity of each of the plurality of channels and selects a data rate for each channel based on the determined capacity. A plurality of transmission subsystems (56-72) are responsive to the control processor (50). Each transmission subsystem is associated with a respective one of the plurality of channels and scrambles the encoded data with channel-specific codes for transmission in the channels. A variable ratio demultiplexer (56), under the control of the control processor (50), demultiplexes the encoded data at a demultiplex rate derived from the data rate selected for the channel by the controller. Put in multiple sending subsystems. In another aspect of the transmission subsystem, the encoded symbols are provided to a symbol repetition means (58) that keeps the symbol rate of the data to be transmitted constant. In yet another aspect, there is no symbol repetition provided, and data rate modulation is performed using a variable length Walsh sequence.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD OF THE INVENTION

The present invention relates to a method and an apparatus for transmitting data in a multi-carrier system. The present invention may be used in spread spectrum communication systems to maximize system throughput and increase signal diversity by dynamically multiplexing the signal onto multiple carriers.

[0002]

[Prior art]

It is desirable to be able to transmit data at a rate higher than the maximum data rate of a single CDMA channel. Conventional CDMA channels (as standardized for cellular communications in the United States) use a 64-bit Walsh spreading function at 1.2288 MHz to carry digital data at a maximum rate of 9.6 bits per second. Can be.

[0003] Many solutions to this problem have been proposed. One solution is to assign a plurality of channels to the user and allow these users to send and receive data in parallel on the available channels. Two methods for providing multiple CDMA channels for use by a single user, filed April 28, 1997, describe a method for providing variable rate data to a communication system using statistical multiplexing. US Patent Application Ser. No. 08 / 431,180 entitled "Reservation and Apparatus" and filed Apr. 16, 1997, for providing variable rate data to a communication system using a non-orthogonal overflow channel. No. 08 / 838,240, which is assigned to the assignee of the present invention and incorporated herein by reference. Further, frequency diversity can be obtained by transmitting data to a plurality of spread spectrum channels that are separated from one another by frequency. A method and apparatus for redundantly transmitting data for multiple CDMA channels is described in US Patent No. 5,166,951 entitled "High Capacity Spread Spectrum Channel"
This patent is incorporated herein by reference.

[0004] The use of code division multiple access (CDMA) modulation is one of several techniques that facilitate communication in which a large number of system users exist. Time division multiple access (T
DMA), frequency division multiple access (FDMA), amplitude-compressed single sideband (ACSSB)
Other multiple access communication system technologies are also known, such as AM modulation schemes such as However, CDMA has significant advantages over these other technologies for multiple access communication systems.

[0005] Multiple access communication systems that use CDMA technology are "Spread Spectrum Multiple Access Communication Systems Using Satellites or Terrestrial Repeaters," assigned to the assignee of the present invention and incorporated herein by reference. US Patent No. 4,901, entitled
No. 307. Those using CDMA technology in a multiple access communication system are assigned to the assignee of the present invention and incorporated herein by reference,
A system and method for generating signal waveforms in a CDMA cellular telephone system is further disclosed in US Patent No. 5,103,459. A code division multiple access communication system is described in "Dual Mode Wideband Spread Spectrum Cellular." It is standardized in the Telecommunications Industry Association Interim Standard IS-95, entitled "Mobile Station-Base Station Compatibility Standard for the System," which is incorporated herein by reference.

[0006] Due to its inherent nature of being a wideband signal, CDMA waveforms provide a form of frequency diversity by spreading signal energy over a wide bandwidth. Therefore, frequency selective fading affects only a small portion of the CDMA signal bandwidth. Spatial or path diversity in the forward / reverse link is obtained by providing multiple signal paths through a synchronous link to or from a mobile user via two or more antennas, cell sectors or cell sites. Further, path diversity can be obtained by exploiting the multipath environment through spread spectrum processing so that signals arriving with different propagation delays can be individually received and processed. Examples of path diversity are both assigned to the assignee of the present invention and incorporated herein by reference,
US Patent No. 5,101,501 entitled "Method and System for Providing Soft Handoff in Communications of a CDMA Cellular Telephone System" and US Patent No. 5,10 entitled "Diversity Receiver in a CDMA Cellular Telephone System"
No. 9,390.

FIG. 1 shows a transmission scheme for a multi-carrier code division multiple access (CDMA) system, where each carrier carries a fixed portion of the transmitted data. The variable rate frame of information bits is provided to encoder 2, which encodes the bits according to a convolutional encoding format. The encoded symbols are provided to a symbol repetition means 4. The symbol repetition means 4 repeats the encoded symbols to provide fixed rate symbols from the symbol repetition means 4 irrespective of the information bit rate.

[0008] The repetitive symbols are provided to a block interleaver 6, which reconstructs a sequence in which the symbols are transmitted. The interleaving process is combined with forward error correction and provides time diversity, which helps in receiving and recovering transmitted signals in the presence of burst errors. The interleaved symbols are provided to data scrambler 12. Data scrambler 12 multiplies each interleaved symbol by +1 or -1 according to a pseudo-noise (PN) sequence. The pseudo-noise sequence is provided by sending the long PN sequence generated by the long code generator 8 at the chip rate through the decimator 10, which deciphers a subset of the long code sequence chips at the rate of the interleaved symbol stream. Selectively provide.

The data from the data scrambler 12 is supplied to a demultiplexer (DEMUX) 14.
Provided to Demultiplexer 14 splits the data stream into three equal sub-streams. The first substream is provided to a transmission subsystem 15a, the second substream is provided to a transmission subsystem 15b, and the third substream is provided to a transmission subsystem 15c. The sub-frames are provided to a serial-to-parallel converter (binary to four levels) 16a-16c. The output of serial-to-parallel converters 16a-16c is a set of four symbols (2 bits / symbol) to be transmitted in QPSK modulation format.

The signals from the serial / parallel converters 16a to 16c are supplied to Walsh coders 18a.
-18c. In the Walsh coder 18a-18c, each converter 16a
The signal from -16c is multiplied by a Walsh sequence consisting of ± 1 values. The Walsh coded data is provided to a QPSK spreader 20a-20c, which spreads the data according to two short PN sequences. The short PN sequence spread signal is provided to an amplifier 22a-22c, which amplifies the signal according to a gain factor.

[0011] The system described above has several disadvantages. First, since the data is provided in equal sub-streams on each carrier, the available numerology is:
The frame is limited to a frame having a plurality of code symbols equally divided by a factor of three. Table 1 below shows a limited number of possible rate sets that can be utilized using the transmission system shown in FIG. Table 1

[Table 1]

As shown in Table 1, since the symbols are evenly distributed over three carriers, the total data rate is limited by the carrier with the lowest available power or requiring the highest SNR. You. That is, the total data rate is equal to three times the data rate of the "lowest" link (where the lowest requires the highest SNR,
Or the one with the lowest available power). This reduces system throughput. The reason is that the lowest link rate is always chosen as the common rate for all three carriers. This results in lower channel resource utilization on the two better links.

Second, frequency-dependent fading has a significant effect on one of the frequencies, but only a limited effect on the remaining frequencies. This configuration is inflexible and it cannot provide frame transmission in a way that reduces the effects of bad channels. Third, due to frequency-dependent fading, fading generally always affects the same group of symbols in each frame. Fourth,
When this configuration is superimposed on a voice transmission system, there is no good way to balance the load imposed on different frequencies on a frame-by-frame basis when there is variable voice activity in each frame. This results in a loss of total system throughput. Fifth, for a system having only three frequency channels, if the configuration described above is adopted, voice and data are separated and one frequency or one
There is no way to provide data on a set of frequencies and voice on a different frequency or a set of frequencies. This results in a loss of system throughput as mentioned earlier.

[0014]

[Problems to be solved by the invention]

Thus, it provides greater flexibility in numerology and load balancing, better solution in supported data rates, and provides better performance in the presence of frequency selective fading and uneven loading There is a need for an improved multi-carrier CDMA communication system

[Means for Solving the Problems]

In one aspect, the present invention provides a transmitter for transmitting data at a data rate on a plurality of channels each having a lower capacity than the data rate, the transmitter determining a capacity of each of the plurality of channels, A controller responsive to the controller for selecting a data rate for each channel based on the determined capacity, each associated with a respective one of the plurality of channels, and transmitting the encoded data to the channels for transmission in the channels. Multiple transmit subsystems scrambling with a unique code, and multiple encoded data demultiplexed at a demultiplex rate derived from the data rate selected for the channel by the controller in response to the controller Variable demultiplexer in the transmission subsystem ; And a support.

[0015] In another aspect, the invention provides a receiver that simultaneously receives, over a plurality of channels, signals that respectively define scrambled encoded symbols that together represent data from a common source. A receiving circuit, a controller for determining a symbol rate for a signal of each channel, and a controller responsive to the controller, each associated with a respective one of the plurality of channels, descrambling the encoded symbols with a channel-specific code to encode the data Multiplexing data from the plurality of receiving systems at a multiplex rate derived from the symbol rate determined for the channel by the controller and responsive to the controller, the plurality of receiving subsystems allowing extraction from the symbols; Variable multiplex to output And

In another aspect, the present invention provides a wireless transmitter, which receives a set of information bits, encodes the information bits to provide a set of code symbols, and a codec. A transmission subsystem that receives the symbols, provides a subset of the code symbols on a first carrier frequency, and provides the remaining symbols on at least one additional carrier frequency.

The present invention also provides a method of transmitting data at a data rate on a plurality of channels each having a lower capacity than the data rate, the method determining the respective capacities of the plurality of channels and determining the determined capacity. Select the data rate for each channel based on capacity, scramble the encoded data with a channel specific code for transmission in the channel, and obtain from the data rate selected for the channel by the controller Demultiplexing involves demultiplexing the encoded data into multiple channels.

The present invention further provides a method for receiving data, the method comprising: simultaneously receiving, on a plurality of channels, respective signals each defining a scrambled encoded symbol representing data from a common source; Determine the symbol rate for the signal in the channel, descramble the encoded symbols in each channel with a channel-specific code so that data can be extracted from the encoded symbols, and obtained from the symbol rate determined for the channel. The multiplex rate includes multiplexing descrambling data from multiple channels.

In order to better utilize channel resources, it is necessary to be able to transmit different data rates on each carrier according to the channel conditions and the power available on each channel. One way to do this is by changing the ratio of the inverse multiplexing on each carrier. Instead of distributing the symbols in a 1: 1: 1 ratio, any arbitrary ratio can be used with different repetition schemes as long as the resulting symbol rate on each carrier is a factor of some Walsh function rate. The Walsh function rate can be 1228800, 614400, 307200,..., 75 for Walsh function lengths from 1 to 16384.

Given a Walsh function length, if the symbol rate is lower than the Walsh function rate, symbol repetition is used to “match” the rate. The repetition factor can be any number, integer, or fraction. It will be understood by those skilled in the art that if repetition is present, the total transmit power is reduced proportionally to keep the code symbol energy constant. Walsh function lengths may or may not be the same on the three carriers, depending on whether code channel needs to be saved. For example, the code symbol rates that can be supported on three channels are (for rate コ ー デ ィ ン グ coding, each is 76.8 kbps
, 15.36 kbps and 51.2 kbps, with a total data rate of 14
153600 sps, 30720 sps and 102)
400 sps, and the reverse multiplex ratio becomes 15: 3: 10.

If a Walsh function of length 8 is used for all three channels (assuming QPSK modulation with a QPSK symbol rate of 153.6 Ksps), each code symbol is transmitted on three channels. They are transmitted twice, ten times and three times, respectively. Additional time diversity can be obtained if repetitive symbols are further interleaved. In alternative embodiments, different Walsh function lengths are used. For example, Walsh functions for three channels in the above examples of 16, 16 and 8, respectively, can be used, where each code symbol is once on the first channel, five times on the second channel, Is transmitted three times on the channel.

The previous approach does not affect the encoder. The reason is that you must be able to handle the highest data rates anyway. It is all about changing the number of data octets at the encoder input. However, this approach has implications for the interleaver configuration. The reason is that this interleaver has many possible sizes (in terms of number of symbols) if all combinations of data rates on the three channels are allowed. One alternative approach to the previous approach that alleviates this problem is to demultiplex the code symbols from the encoder directly onto three carriers and perform interleaving of the repetitive code symbols on each channel independently. .
This simplifies numerology and reduces the number of possible interleave sizes on each channel.

[0023]

BEST MODE FOR CARRYING OUT THE INVENTION

Referring to FIG. 2, which is a block diagram illustrating a transmission system implementing the present invention, the first operation performed is to determine the amount of data that can be supported on each carrier. Although three of these carriers are shown in FIG. 2, those skilled in the art will recognize that the present invention can be readily extended to any number of carriers. The control processor 50 determines the load on each carrier, the amount of data queued for transmission to the base station, and the priority of the information transmitted to the base station.
A data transmission rate on each carrier is determined based on the set of factors.

After selecting a data rate to be transmitted on each carrier, control processor 50 selects a modulation format that can transmit data at the selected data rate. In an exemplary embodiment, Walsh sequences of different lengths are used,
Modulate the data depending on the rate of the transmitted data. The use of Walsh sequences of different lengths selected to modulate data depending on the rate of data transmitted has been filed May 28, 1996, entitled "High Rate Data Wireless Communication System". Patent application Ser. No. 08 / 654,44, pending.
No. 3, which is described in detail, which is assigned to the assignee of the present invention and incorporated herein by reference. In an alternative embodiment, high rate data may be supported by bundling CDMA channels as described in the above-referenced patent applications 08 / 431,180 and 08 / 838,240. it can.

Once the rates supported on each carrier are selected, control processor 50 calculates the inverse multiplex ratio, which determines the amount of each transmission carried on each carrier. For example, the code symbol rates that can be supported on three channels are 153600 sps, 30720 sps, and 1024
00sps (for 1/2 coding, these are 76.8 kbps, 15.
36 kbps and 51.2 kbps respectively, and the total data rate is 14
3.36 kbps), the reverse multiplex ratio is 15: 3: 1.
It becomes 0.

In the exemplary embodiment, a frame of information bits is provided to a frame formatter 52. In the exemplary embodiment, formatter 52 includes a set of cyclic redundancy checks (
Generate a CRC) bit and apply this to the frame. Further, formatter 52 adds a predetermined set of tail bits. The construction and design of frame formatters are well known in the art, and a typical example of a frame formatter is the United States entitled "Methods and Systems for Aligning Vocoder Data to Mask Transmission Channels with Errors." This is described in detail in US Pat. No. 5,600,754, which is assigned to the assignee of the present invention and incorporated herein by reference.

The formatted data is provided to encoder 54. In the exemplary embodiment, encoder 54 is a convolutional encoder, but the invention can be extended to other forms of encoding. The signal from control processor 50 indicates to encoder 54 the number of bits to be encoded in this transmission cycle.
In the exemplary embodiment, encoder 54 is a rate 1/4 convolutional encoder with a constraint length of 9. It should be noted that essentially any encoding format can be used due to the additional flexibility provided by the present invention.

The encoded symbols from the encoder 54 are sent to the variable ratio demultiplexer 5
6 is provided. Variable ratio demultiplexer 56 provides the encoded symbols to a set of outputs based on the symbol output signal provided by control processor 50. In the exemplary embodiment, there are three carrier frequencies and the control processor 50
Provides a signal indicating the number of encoded symbols to be provided at each of the three outputs. As those skilled in the art will appreciate, the present invention can be easily extended to any number of frequencies.

The encoded symbols provided at each output of the variable ratio demultiplexer 56 are provided to corresponding symbol repetition means 58a-58c. Symbol repetition means 58a
Since -58c generates a repeated version of the encoded symbols, the resulting symbol rate matches the rate of data supported on that carrier,
In particular, it matches the Walsh function rate used on that carrier. Repetition generator 5
The construction of 8a-58c is known in the art and such an example is described in detail in U.S. Pat. No. 5,629,955 entitled "Variable Response Filter", which is assigned to the present invention. Assigned to a person and incorporated herein by reference. Control processor 50 provides an independent signal to each of the repetition generators 58a-58c, which indicates the rate of the symbols on each carrier, or alternatively indicates the amount of repetition to be provided on each carrier. In response to signals from control processor 50, symbol repetition means 58a-58c generate as many repetitive symbols as necessary to provide the designated symbol rate. It should be noted that in the preferred embodiment, the number of repetitions is not limited to an integer such that all symbols are repeated the same number of times. A method for providing non-integer repetition is described in detail in US patent application Ser. No. 08 / 886,815, filed Mar. 26, 1997, entitled "Method and Apparatus for Transmitting High Speed Data in Spread Spectrum Communication Systems." This patent application is assigned to the assignee of the present invention and is hereby incorporated by reference.

The symbols from the repetition generators 58a-58c correspond to one corresponding interleaver 6
0a-60c, the interleavers 60a-60c reorder the repetition symbols according to a predetermined interleaver format. The control processor 50 transmits the interleave format signal to each of the interleavers 60a-60.
c, which indicates one of a predetermined set of interleaving formats. In an exemplary embodiment, the interleaving format is selected from a predetermined set of bit de-interleaving formats.

[0031] The reordered symbols from interleavers 60a-60c are provided to data scramblers 62a-62c. Each data scrambler 62a-62c
Changes the sign of the data according to a pseudo-noise (PN) sequence. Each P
The N sequence is provided by passing the long code at the chip rate or the long PN code generated by PN generator 82 through decimators 84a-84c. Decimators 84a-84c selectively provide some spreading symbols to provide a PN sequence at a rate no higher than that provided by PN generator 82. Since the symbol rates on each carrier are different from each other, the decimation rates of the decimators 84a-84c may be different. Decimators 84a-84c are sample and hold circuits that sample the PN sequence from PN generator 82 and continue to output their values for a predetermined period. The construction of PN generator 82 and decimators 84a-84c is well known in the art and is described in detail in the above-mentioned U.S. Pat. No. 5,103,459. The data scramblers 62a-62c are
XOR the binary symbols from a-60c with the decimated pseudo-noise binary sequences from decimators 84a-84c.

The binary scrambled symbol sequence is provided to serial-to-parallel converters (binary to four levels) 64a-64c. The two binary symbols provided to the converters 64a-64c are mapped into a quartet arrangement having values (± 1, ± 1). The constellation values are provided to two outputs from converters 64a-64c. The symbol streams from converters 64a-64c are separately separated by Walsh spreader 6
6a-66c.

There are many ways to provide high speed data to a code division multiple access communication system. In a preferred embodiment, the length of the Walsh sequence is varied according to the rate of the data to be modulated. A shorter Walsh sequence is used to modulate high speed data, and a longer Walsh sequence is used to modulate lower rate data. For example, 19.2 using a 64-bit Walsh sequence
Data can be transmitted at Ksps. However, data can be modulated at 38.4 Ksps using a 32-bit Walsh sequence.

A system describing variable-length Walsh sequence modulation is filed on January 15, 1997 and entitled “High Data Rate Auxiliary Channel for CDMA Communication Systems”.
No. 08 / 724,281, which is incorporated herein by reference, which is incorporated herein by reference. The length of the Walsh sequence used to modulate the data is based on the rate of the transmitted data. FIG. 4 shows a Walsh function in a conventional IS-95 CDMA system.

In a preferred embodiment of the present invention, the number of Walsh channels allocated for high rate data can be any number 2 ^N , where N = {2,3,4,5,6 ｝. The Walsh code used by Walsh Coders 66a-66c is not the 64 symbols used in the IS-95 Walsh Code,
64/2 ^N symbol length. For high rate channels orthogonal to other code channels with 64 symbol Walsh codes, 2 ^N out of 64 possible 4 phase channels with 64 symbol Walsh are excluded from use. Table 2 shows the assigned Walsh codes and corresponding sets of assigned 6 for each of the N values.
A list of 4 symbol Walsh codes is provided. Table 2

[Table 2]

+ And-represent positive or negative integer values, and a preferable integer is 1. As can be seen, the number of Walsh symbols in each Walsh code changes as N changes, and in all examples is less than the number of symbols in the IS-95 Walsh channel code. Regardless of the length of the Walsh code, in the described embodiment of the invention, the symbols are utilized at a rate of 1.2288 megachips per second (Mcps). Thus, shorter length Walsh codes are repeated more frequently. Control processor 50 provides signals indicating Walsh sequences used to spread the data to Walsh coding elements 66a-66c.

[0037] Alternative methods of transmitting high rate data in a CDMA communication system include those commonly referred to as channel bundling techniques. The present invention is a CD
The present invention is equally applicable to a channel bundling method for providing high-speed data in an MA communication system. One way to provide channel-bundled data is
To provide multiple Walsh channels for use by signaling users. This method is described in detail in the above-referenced US patent application Ser. No. 08 / 739,482. An alternative channel bundling method is for the user to use one Walsh code channel, but different scrambled signals, as described in detail in pending US patent application Ser. No. 08 / 838,240. Is to make the signal different from the others.

The Walsh spread data is provided to PN spreaders 68a-68c, which apply short PN sequence spreading to the output signal. In an exemplary embodiment, PN spreading is performed using the previously mentioned pending US patent application Ser.
It is performed by complex multiplication as described in detail in U.S. Pat. Data channels D _I and D _Q are, as a first real number term and imaginary terms respectively, and as a second real number term and imaginary terms respectively, are complex multiplication and spreading codes PN _I and PN _Q, in phase (i.e., real) generating a term X _I and quadrature (i.e., the imaginary) term X _Q. Spreading codes PN _I and PN _Q are generated by spreading code generator 67 and 69. Spreading codes PN _I and PN _Q are utilized in 1.2288 Mcps. Equation (1) shows the complex multiplication performed. _{(X I + jX Q) =} (D I + jD Q) (PN I + jPN Q) (1)

The in-phase term X _I is a low-pass filter is (not shown) the bandwidth of 1.2288 MHz, is up- Bad is multiplied by in-phase carrier COS (ω _c t). Similarly, quadrature phase term X _Q is also (not shown) are low-pass filtered is the bandwidth of 1.2288 MHz, it is multiplied with the quadrature-phase carrier SIN (omega _c t) by up-conversion. Upconverted X _I and X _Q terms are summed, the forward link signal s (t) is generated. Complex multiplication allows the quadrature channel set to remain orthogonal to the in-phase channel set, and thus, with perfect receiver phase recovery, adds to other channels transmitted on the same path A quadrature channel set can be provided without adding substantial interference.

The PN spread data is provided to filters 70a-70c, which
70c spectrally shapes the signal for transmission. The filtered signal is provided to gain multipliers 72a-72c. The gain multipliers 72a-72c amplify the signal for each carrier. The gain coefficient is controlled by the control processor 50 to control the gain element 7.
2a-72c. In an exemplary embodiment, control processor 50 selects a gain factor for each carrier according to channel conditions and the rate of information data to be transmitted on the carrier. As is known to those skilled in the art, data transmitted repeatedly may be transmitted at lower symbol energy than data without repetition.

The amplified signal is provided to an optional switch 74. This switch 7
4 provides the additional flexibility of the channel to hop data signals to different carriers. Typically, switch 74 is used only when the number of carriers actually used to transmit the signal is less than the total number of possible carriers (3 in this example).

The data is sent by switch 74 to carrier modulators 76a-76c. Each carrier modulator 76a-76c upconverts the data to a different predetermined frequency. The upconverted signal is provided to a transmitter 78 where the signal is combined with other similarly processed signals, filtered, and amplified for transmission through antenna 80. In an exemplary embodiment, the amplification frequency at which each signal is transmitted changes over time. This provides additional frequency diversity for the transmitted signal. For example, the signal currently being transmitted through the carrier modulator 76a is switched at a predetermined time interval so that it is transmitted at a different frequency through the carrier modulator 76b or 76c. In accordance with the signal from control processor 50, switch 74 directs the amplified input signal from gain multipliers 72a-72c to the appropriate carrier modulators 76a-76c.

Turning to FIG. 3, a receiving system implementing the present invention is shown. The signal received by the antenna 100 is sent to a receiver (RCVR) 102,
2 amplifies and filters the signal before providing it to switch 104. The data is provided through switch 104 to the appropriate carrier demodulators 106a-106c. Although the receiver structure is described for the reception of signals transmitted on three frequencies, it is to be understood that the present invention can be easily extended to any number of frequencies that are contiguous or non-contiguous. The trader will understand.

Switch 104 responds to a control signal from control processor 125 to convert the received signal to a selected carrier demodulation when the carrier on which the data is transmitted is rotated or hopped to provide additional frequency diversity. To the vessels 106a-106c. If the carrier frequency is not hopped or rotated, switch 104 is unnecessary. Each carrier demodulator 106a-106c uses a different down-conversion frequency to convert the received signal to baseband by 1/4 phase shift keying (QP
SK) to provide independent I and Q baseband signals.

The downconverted signal from each carrier demodulator 106a-106c is provided to a corresponding PN despreader 108a-108c, which
-108c removes short code spreading from the downconverted data. The I and Q signals are despread by complex multiplication with a pair of short PN codes. The PN despread data is provided to a Walsh demodulator 110a-110c, which uncovers the data according to an assigned code channel sequence. Although the exemplary embodiment uses Walsh functions for generating and receiving CDMA signals, other forms of code channel generation are equally applicable. Control processor 125 provides a signal indicative of the Walsh sequence used to uncover the data to Walsh demodulator 110a-
110c.

The Walsh despread symbols are provided to parallel-to-serial converters (4-level to binary) 112a-112c, which
a-112c maps a two-dimensional signal into a one-dimensional signal. The symbols are provided to descramblers 114a-114c. The descramblers 114a-114c descramble the data according to the decimated long code sequence generated as described for the decimated long code sequence used to scramble the data in FIG.

The descrambling data is a deinterleaver (DE-INT) 116 a-116.
c. The deinterleaver 116a-116c controls the control processor 12
Reorder the symbols according to the selected deinterleaver format provided by 5. In the exemplary embodiment, control processor 125 sends a signal indicating the size of the deinterleaver and the deinterleave scheme to each deinterleaver 1.
16a-116c. In an exemplary embodiment, the deinterleaving scheme is selected from a predetermined set of bit de-interleaving schemes.

The deinterleaved symbols are provided to symbol combiners 118a-118c, which combine these repetitively transmitted symbols coherently. The combined symbols (soft decisions) are provided to variable ratio multiplier 120, which reassembles the data stream and provides the reassembled data stream to decoder 122. In the exemplary embodiment, decoder 122 is a maximum likelihood decoder, the configuration of which is well known in the art. In the exemplary embodiment, decoder 122 comprises a buffer (not shown), which waits until data for the entire frame has been provided before starting the decoding process. The decoded frame is provided to a CRC checking means 124, which determines whether the CRC bits match, and if so, provides the decoded frame to the user;
Otherwise, erasure is declared.

Although the present invention has been described by reference to a preferred embodiment, this embodiment is exemplary only and modifications and variations that occur to those having the appropriate knowledge and skills are not claimed. It will be appreciated that modifications may be made without departing from the spirit and scope of the invention as set forth in the scope and equivalents thereof.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a multi-frequency CDMA communication system having a fixed rate and a carrier.

FIG. 2 is a block diagram illustrating a transmission system implementing the present invention.

FIG. 3 is a block diagram illustrating a receiving system implementing the present invention.

FIG. 4 is a table of code channel Walsh symbols in a conventional IS-95 CDMA communication system.

──────────────────────────────────────────────────続 き Continuation of front page (81) Designated country EP (AT, BE, CH, CY, DE, DK, ES, FI, FR, GB, GR, IE, IT, LU, MC, NL, PT, SE ), OA (BF, BJ, CF, CG, CI, CM, GA, GN, GW, ML, MR, NE, SN, TD, TG), AP (GH, GM, KE, LS, MW, SD, SZ, UG, ZW), EA (AM, AZ, BY, KG, KZ, MD, RU, TJ, TM), AL, AM, AT, AU, AZ, BA, BB, BG, BR, BY, CA, CH, CN, CU, CZ, DE, DK, EE, ES, FI, GB, GE, GH, GM, HR, HU, ID, IL, IS, JP, KE, KG, KP , KR, KZ, LC, LK, LR, LS, LT, LU, LV, MD, MG, MK, MN, MW, MX, NO, NZ, PL, PT, RO, RU, SD, SE, SG, SI, SK, SL, TJ, TM, TR, TT, UA, UG, UZ, VN, YU, ZW [Summary Conclusion] has no symbol repetition provided and uses a variable length Walsh sequence Perform rate modulation.

Claims (39)

[Claims] A transmitter for transmitting data at a data rate on a plurality of channels each having a capacity lower than the data rate, wherein a capacity of each of the plurality of channels is determined, and data for each channel is determined based on the determined capacity. A controller for selecting a rate, responsive to the controller, each associated with a respective one of the plurality of channels,
A plurality of transmission subsystems for scrambling the encoded data with channel-specific codes for transmission in the channel, and a demultiplexer responsive to the controller and derived from the data rate selected for the channel by the controller. A variable demultiplexer that demultiplexes the encoded data into a plurality of transmission subsystems at a plex rate. 2. The transmitter according to claim 1, further comprising an encoder for generating encoded data from the input data frame. 3. The transmission according to claim 1, wherein each transmission subsystem comprises a symbol repetition unit for repeating symbols to output the same at a rate corresponding to the rate selected for the channel by the controller. Machine. 4. The transmitter of claim 3, wherein each transmission system comprises an interleaving unit that reorders repetition symbols based on an interleaving format determined by the controller. 5. A long code generator for generating a long code for each channel, respectively, and a scrambler in each transmission subsystem that scrambles the reordered symbols using each code for the channel. 5. The transmitter according to claim 4, further comprising: 6. A long code generator for each channel, comprising a decimator unit for decimating the generated long code to generate each long code for each channel at a decimating rate determined by the controller. The transmitter according to claim 5. 7. The system of claim 6, further comprising a variable coding unit in each modulation subsystem for modulating the scrambled symbols from the scrambler.
The transmitter described. 8. The transmitter of claim 7, wherein the coding unit is configured to demodulate the scrambled symbols with each Walsh code. 9. The transmitter of claim 7, further comprising a pseudo-noise spreader in each channel that spreads the modulated symbols. 10. A plurality of carriers, further comprising a switch and a plurality of carrier modulators, wherein the switch is responsive to the controller and modulates scrambled data from the plurality of transmission subsystems to different carriers at different times. The transmitter according to any one of claims 1 to 9, wherein switching is performed between modulators. 11. A receiving circuit for simultaneously receiving, on a plurality of channels, respective signals each defining a scrambled encoded symbol representing data from a common source, a controller for determining a symbol rate for the signals on each channel, Responding to the controller, each associated with a respective one of the plurality of channels,
A plurality of receiving subsystems that descramble the encoded symbols with a channel-specific code so that the data can be extracted from the encoded symbols, and that are responsive to the controller and derived from a symbol rate determined for the channel by the controller. A variable multiplexer that multiplexes and outputs data from a plurality of receiving systems at a multiplex rate. 12. The receiver according to claim 11, further comprising a decoder for decoding the encoded data output from the multiplexer into frame data. 13. The receiver according to claim 11, further comprising a pseudo noise despreader in each channel for despreading the scrambled encoded symbols. 14. The receiver according to claim 13, further comprising a variable decoding unit in each receiving system for demodulating the despread symbols from the despreader. 15. The receiver of claim 14, wherein the decoding unit is configured to demodulate the despread symbols with each Walsh code. 16. The receiver of claim 15, further comprising a descrambler in each receiving subsystem to descramble the despread symbols using each long code for the channel. 17. The receiver of claim 16, wherein each receiver subsystem comprises a deinterleaver unit for reordering repetition symbols based on an interleave format determined by a controller. 18. Each receiving subsystem includes a symbol combiner that combines symbols at a rate corresponding to the rate determined for the channel by the controller and outputs the same to a demultiplexer. 17. The receiver according to 17. 19. A switch and a plurality of carrier demodulators, the switch responsive to a controller for demodulating a signal between the plurality of carrier demodulators for input to different receiving subsystems at different times. The receiver according to any one of claims 11 to 18, which switches a reception signal. 20. An encoder for receiving a set of information bits, encoding the information bits to provide a set of code symbols, receiving an code symbol, providing a subset of the code symbols to a first carrier frequency, and A transmission subsystem that provides the symbols of at least one additional carrier frequency. 21. A method for transmitting data at a data rate on a plurality of channels each having a capacity lower than the data rate, comprising determining a capacity of each of the plurality of channels and determining a data rate for each channel based on the determined capacity. And scrambling the encoded data with a channel-specific code for transmission in the channel, and encoding the encoded data at a demultiplex rate derived from the data rate selected for the channel by the controller. A method of demultiplexing data into multiple channels. 22. The method according to claim 21, further comprising an encoder for generating encoded data from the input data frame. 23. The method of claim 21 further comprising repeating symbols for each channel to output the same at a rate corresponding to the rate selected for the channel. 24. The method of claim 23, further comprising reordering repetition symbols based on the determined interleaving format. 25. The method of claim 24, wherein a long code is generated for each channel, and each code for the channel is used to scramble the reordered symbols in each transmission subsystem. 26. The method of claim 25, wherein at the decimating rate determined for each channel, long codes are generated for each by decimating the generated long codes. 27. The method of claim 26, further comprising modulating the scrambled symbols with a code. 28. The method of claim 27, wherein each Walsh code demodulates a scrambled symbol. 29. The method of claim 27 or claim 28, further comprising spreading the modulated symbols with pseudo noise. 30. The method according to any one of claims 21 to 29, further comprising modulating the scrambled data on different carriers at different times. 31. A method for receiving data, comprising simultaneously receiving, on a plurality of channels, respective signals each defining a scrambled encoded symbol representing data from a common source, and determining a symbol rate for the signals on each channel. And descrambling the encoded symbols in each channel with a channel-specific code so that data can be extracted from the encoded symbols. Multiplex rates derived from the symbol rate determined for the channel can be used for multiple channels. Data receiving method for multiplexing descrambling data from 32. The data receiving method according to claim 31, further comprising decoding the multiplexed encoded data into frame data. 33. The data receiving method according to claim 31, further comprising despreading the scrambled encoded symbols using a pseudo noise code. 34. The data receiving method according to claim 33, further comprising demodulating a despread symbol by variable decoding. 35. The data receiving method according to claim 34, wherein a despread symbol is demodulated by each Walsh code. 36. The method of claim 35, further comprising descrambling the despread symbols in each channel using each long code for the channel. 37. The method of claim 36, further comprising reordering repetition symbols based on the determined interleaving format. 38. Combining symbols in a channel before demultiplexing the same at a rate corresponding to the rate determined for the channel.
7. The data receiving method according to 7. 39. The data receiving method according to claim 31, further comprising demodulating signals in different channels at different times.